Hydraulic unit supported in such a way as to damp vibration and forming part of a slip-controlled brake system

ABSTRACT

A vibration damping arrangement for improving the structure-borne noise isolation of a hydraulic unit forming part of a slip-controlled brake system from a vehicle. The hydraulic unit is supported elastically on the vehicle, below its center of gravity, on three rubber spring elements. In this arrangement, the rubber spring elements are situated both in front of and behind a vertical projection of the center of gravity and symmetrically in and on both sides of a vertical plane passing through the center of gravity. In addition, the three rubber spring elements are arranged along the lateral surface of an imaginary circular cylinder, on the horizontally extending longitudinal axis of which the center of gravity of the hydraulic unit lies. The rubber spring elements are formed of disk springs, the ends of which, carry fastening elements, extend approximately tangentially to the lateral surface of the imaginary circular cylinder.

PRIOR ART

The invention relates to a hydraulic unit which is supported in such away as to damp vibration of a slip-controlled brake system.

Such a vibration-damping support system for a hydraulic unit in avehicle has already been disclosed (DE-C-39 41 401). In this supportsystem, the housing of the hydraulic unit is provided on opposite endfaces with three horizontally extending studs, each of which engages ina rubber shaped part seated in a cap-shaped component connected to thebody of the vehicle. During slip control, vibrations of the hydraulicunit, particularly those excited by the reciprocating-piston pump, arenot fully damped since the rubber shaped parts are subjected essentiallyto compressive stress.

ADVANTAGES OF THE INVENTION

In contrast, the hydraulic unit is supported in accordance with theinvention in such a way as to damp vibration has the advantage that the. . . rubber spring elements are subjected primarily to shear during theoperation of the pump, i.e. in a manner in which the lower springrate--as compared with compressive or tensile stress--characteristic ofrubber is exploited. This improves the effectiveness with which thetransmission of structure-borne noise from the hydraulic unit to thevehicle body is isolated.

The development of the invention specified herein increases the degreeof assembly of the hydraulic unit and facilitates installation in thevehicle. In addition, incorrect mounting of the rubber spring elementsis avoided.

BRIEF DESCRIPTION OF THE DRAWINGS

An exemplary embodiment of the invention is illustrated in simplifiedform in the drawing and explained in greater detail in the followingdescription. FIG. 1 shows an end view of a hydraulic unit with thearrangement of rubber spring elements and FIG. 2 shows a side view ofthe hydraulic unit in the direction of arrow II in FIG. 1.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENT

The hydraulic unit 10 illustrated in FIGS. 1 and 2 of the drawing ispart of a slip-controlled brake system (not shown) of a vehicle,especially a passenger vehicle. The hydraulic unit 10 has a housing 11with the approximate shape of a cuboid standing on an edge. An electricdrive motor 13 is attached to a vertical end face 12 of the housing 11.The motor 13 serves to drive in rotation an eccentric shaft 15 arrangedwith its longitudinal axis 14 horizontal. Engaging on said shaft on bothsides are respective reciprocating pistons 16 and 17 ofreciprocating-piston pumps 18 and 19. The horizontally extendinglongitudinal axes 20 of the reciprocating-piston pumps 18 and 19arranged in the housing 11 of the hydraulic unit 10 intersect thelongitudinal axis 14 of the eccentric shaft 15 at right angles. Thecenter of gravity 21 of the hydraulic unit 10 is at a distance above thelongitudinal axis 20, within the housing 11, in a vertical plane 22passing through the shaft longitudinal axis 14. The hydraulic unit 10 isaccordingly excited into torsional vibrations in the direction of thedouble arrow 23 indicated in FIG. 1 about the center of gravity 21 bythe reciprocating pistons 16 and 17, which are driven in translation.

A twin angle bracket 26 formed from sheet metal is fastened to themotor-side end face 12 of the housing 11. A single angle bracket 28 madeof sheet metal is bolted to the opposite end face 27 of the housing 11(FIG. 2). As shown, the twin angle bracket 26 and the single anglebracket 28 can be connected to one another by a link 29. A holder 30designed as a sheet-metal shaped part is furthermore illustrated at adistance underneath the hydraulic unit 10. This holder is designed (in amanner not shown) to be fastened to the vehicle. Two rubber springelements 31 and 32 are arranged between the double angle bracket 26 andthe holder 30, and one rubber spring element 33 is arranged between thesingle angle bracket 28 and the holder 30. At their ends 34 and 35, therubber-spring elements 31 to 33, which are designed as rubber-metalsprings in the form of disk springs, are screwed to the twin anglebracket 26 and single angle bracket 28, on the one hand, and to theholder 30, on the other hand, by fastening means 36 in the form of boltsand nuts. As seen in the direction of the shaft longitudinal axis 14 inFIG. 1, the three rubber spring elements 31 to 33 are arranged both infront of (31, 32) and behind (33) a vertical projection of the center ofgravity 21 and also symmetrically in (33) and on both sides of (31, 32)the vertical plane 22. As can also be seen from FIG. 1 of the drawing,the three rubber spring elements 31 to 33 are furthermore arranged alongthe lateral surface 39 of an imaginary circular cylinder, on thelongitudinal axis 40 of which, said longitudinal axis runninghorizontally and being parallel to the shaft longitudinal axis 14, thecenter of gravity 21 of the hydraulic unit 10 lies. In this arrangement,the ends 34 and 35 of the rubber spring elements 31 to 33 extendapproximately tangentially to the lateral surface 39 of the imaginarycircular cylinder.

The hydraulic unit 10 is thus supported elastically and in a stablemanner on the vehicle by three rubber spring elements 31 to 33 below itscenter of gravity 21. Under excitation by the motor-drivenreciprocating-piston pumps 18 and 19, it can vibrate about thelongitudinal axis 40 of the circular cylinder, along the lateral surface39 of which the rubber spring elements 31 to 33 are arranged. In thisarrangement, the rubber spring elements 31 to 33 are subjected toparallel shear stress and, as a result, effective damping of thevibratory motion of the hydraulic unit 10 in the direction of the doublearrow 23 is achieved by virtue of the low spring rate of rubber as amaterial. Since the resonant frequency of the rubber spring elements 31to 33 in relation to the excitation frequency of the hydraulic unit 10is low, this leads to good structure-borne noise isolation of thehydraulic unit from the vehicle.

The foregoing relates to preferred exemplary embodiments of theinvention, it being understood that other variants and embodimentsthereof are possible within the spirit and scope of the invention, thelatter being defined by the appended claims.

I claim:
 1. A hydraulic unit (10) which is supported in such a way as todamp vibration and forms part of a slip-controlled brake system of apassenger vehicle, having at least one reciprocating-piston pump (18,19) with reciprocating pistons (16, 17) in whicha longitudinal axis (20)of the reciprocating piston (16, 17) of the pump (18, 19), which isactuated by a rotating, horizontally extending eccentric shaft (15),runs at a distance from a center of gravity (21) of the hydraulic unit(10), the housing (11) of the hydraulic unit (10) is supportedelastically on the vehicle by three rubber spring elements (31, 32, 33),in relation to a vertical plane (22) passing through the center ofgravity (21) and the longitudinal axis (14) of the eccentric shaft (15),the rubber spring elements (31, 32, 33) are, as seen in a direction of ashaft longitudinal axis (14), arranged both in front of and behind avertical projection of the center of gravity (21) and symmetrically andon both sides of a vertical plane (22), the three rubber spring elements(31, 32, 33) are arranged below a center of gravity (21) of thehydraulic unit (10), the three rubber spring elements (31, 32, 33) arearranged along a lateral surface (39) of an imaginary circular cylinder,on the horizontally extending longitudinal axis (40), which also runsparallel to the longitudinal axis (14) of the eccentric shaft (15), ofwhich the center of gravity (21) of the hydraulic unit (10) lies, therubber spring elements (31, 32, 33) are formed of disk springs, the ends(34, 35) of the rubber spring elements carry fastening means (36) whichextend approximately tangentially to the lateral surface (39) of theimaginary circular cylinder.
 2. The hydraulic unit as claimed in claim1, wherein the rubber spring elements (31, 32, 33) are fastened to thehousing (11) of the hydraulic unit (10) and are connected to a holder(30) formed of a sheet-metal shaped part which is intended for fasteningto the vehicle.